Like adolescents, young adults are at risk of initiating tobacco use and escalating to daily use and tobacco dependence. However, not every young adult who uses cigarettes intermittently becomes tobacco dependent, and the time-course of those who transition to daily use varies widely. Individual differences likely contribute to the variability observed in patterns of tobacco use. This project will use a multi-modal research approach to examine dimensions of impulsivity and characteristics of alcohol that are associated with vulnerability for escalation of cigarette smoking, and how alcohol interacts with behavioral inhibition to increase cigarette consumption. Furthermore, this project will support the applicant's career goal of becoming an independent investigator in the field of behavioral pharmacology capable of identifying and understanding risk factors associated with vulnerability to drug use and dependence. Impulsivity is a multidimensional construct that can be assessed using trait measures and tasks of behavioral inhibition, and it is likely that these assessments inform drug use vulnerability. Dimensions of impulsivity are differentially associated with tobacco initiation, escalation, and dependence. Moreover, behavioral inhibition is altered as a consequence of acute and chronic drug exposure. Alcohol is also closely associated with vulnerability to escalating tobacco use, and acute alcohol exposure is associated with decrements in behavioral inhibition. Thus it is likely that impulsivity and alcohol use have separate and combined influences on vulnerability to tobacco use. The first study will utilize data from a longitudinal study to identify trajectories of tobacco use in young adults in order to determine 1) which dimensions of impulsivity and alcohol use inform vulnerability to escalating tobacco use, and 2) if measures of behavioral inhibition are altered as a consequence of escalating cigarette use. The second study will utilize a laboratory design to examine whether alcohol-induced impairments in behavioral inhibition mediate the relationship between acute alcohol administration and increases in ad-libitum cigarette consumption. Results from these studies will improve scientific knowledge by elucidating the relationship between individual differences in both impulsivity and characteristics of alcohol use and escalation of cigarette smoking and identifying the mechanism(s) responsible for alcohol-induced escalation of tobacco use. This knowledge will help inform screening and prevention efforts aimed at reducing the amount of young adults who escalate to daily smoking.